The role of dopamine in temporal memory averaging

Research has previously demonstrated that rats trained with two different cue-duration relations (e.g., tone = 10s, light = 20s) will respond at a time in between the two reinforced times when presented with a compound (tone + light) cue, a phenomenon known as temporal memory averaging (D.N. Swanton, C.M. Gooch & M.S. Matell, 2009). However, as the duration-relations become more disparate (e.g., 10s/30s) a modality effect emerges; wherein, we see temporal averaging in the tone-short/light-long condition, but not in the light-short/tone-long condition. Here, we examine how dopamine affects responding to the compound cue. In accordance with R.D. Oades's (1985) dopamine switching hypothesis, we predicted that administration of haloperidol (0.025 mg/kg) or d-amphetamine (1.0 mg/kg) prior to compound testing will increase averaging in light-short rats and decrease averaging in tone-short rats, respectively. Although d-amphetamine led to a loss of temporal control, haloperidol administration led to increased averaging in light-short rats. These results suggest that dopamine activity influences responding when multiple stimuli are presented simultaneously.